Uplink Transmission Timing Control

ABSTRACT

One or more embodiments herein relate to a method for an uplink transmission timing adjustment in a wireless communication device served by a network node and configured to operate in a coverage enhancement mode. The coverage enhancement mode comprises a repetitive transmission of a first uplink signal during a first repetition period. The method comprises determining a change in a downlink timing ( 210 ), determining whether the first repetition period is ongoing ( 240 ); and in response to the change in the downlink timing and the first repetition period being ongoing, performing an adjustment of an uplink transmission timing outside the first repetition period ( 260 ).

RELATED APPLICATION

The present application claims the benefit of and priority toInternational Patent Application Serial No. PCT/CN2016/078095, filed 31Mar. 2016, the entire contents of which are incorporated herein byreference.

TECHNICAL FIELD

Embodiments of the disclosure generally relate to the field of wirelesscommunication, and more specifically, to uplink transmission timingcontrol in a wireless communication device, such as an EvolvedMachine-type communication (eMTC) device and/or a NarrowbandInternet-of-things (NB-IoT) device.

BACKGROUND

Current specifications for the wireless system standardized by themembers of the 3^(rd)-Generation Partnership (3GPP) and referred to as“Long Term Evolution of UMTS (LTE)” (LTE) allow a wireless communicationdevice to modify the uplink transmission timing in response to adetected change in serving cell downlink timing, provided that suchmodifications are carried out gradually according to rules specified in3GPP TS 36.133 V12.7.0, Section 7.1.2. For example, for non-initialtransmission and an LTE bandwidth of 1.4 MHz (minimum sample rate 1.92MS/s):

-   -   maximum timing adjustment in one correction shall not exceed        17.5 TS (0.6 μs),    -   minimum aggregated adjustment rate shall be 7 TS (0.2 μs) per        second, and    -   maximum aggregated adjustment rate shall be 17.5 TS (0.6 μs) per        200 milliseconds (ms).        The network node may send timing advance commands (TACs) to the        wireless communication device to adjust the uplink transmission        timing in order to have the uplink signals arrive at the network        node receiver at the desirable point in time.

When wireless communication devices operate in a coverage enhancementmode, wherein the coverage enhancement is provided by messagerepetition, the timing advance control loop latency becomes longer thanin conventional LTE system operation. This is because the uplinkreference signals from multiple subframes may have to be averaged orfiltered by the network node, to determine channel estimates from whichthe misalignment with respect to the desirable signal reception time canbe determined. Additionally, when a half-duplex frequency-divisionduplexing (HD-FDD) configuration is used by the wireless communicationdevice (e.g., in HD-FDD eMTC and/or NB-IoT devices), the network nodehas fewer opportunities to send TACs to the device. Particularly, duringan uplink transmission period, the wireless communication deviceoperating in HD-FDD configuration will not listen to the downlink andtherefore is out of reach for the network node until tuning back to adownlink reception period.

As it is unspecified how and when the wireless communication device willadjust its timing when operating in enhanced coverage and in particularwhen uplink signals are transmitted with a certain number ofrepetitions, the existing rules in 3GPP TS 36.133 V12.7.0, Section 7.1.2cannot be applied for any device (e.g., eMTC, NB-IoT devices etc) thatis operating in an enhanced coverage mode and employing repetitions ofthe uplink signal transmission.

SUMMARY

An object of some of the techniques and apparatuses described in detailbelow obviate at least one of the above disadvantages and provideimproved communication between a wireless communication device, such aseMTC or NB-IoT, and a network node in a wireless communication system.According to a first aspect of the techniques described herein, one ormore of the objects are achieved by a wireless communication system. Thesystem comprises a wireless communication device configured to operatein a coverage enhancement mode comprising a repetitive transmission of afirst uplink signal during a first repetition period, and a network nodeserving the wireless communication device. The network node comprises atransmitting unit for transmitting a reference signal to the wirelesscommunication device. The wireless communication device comprises afirst determining unit configured to determine a change in a downlinktiming based on the reference signal, a second determining unitconfigured to determine whether the first repetition period is ongoingand an adjusting unit configured to, in response to the change in thedownlink timing and the first repetition period being ongoing, performan adjustment of an uplink transmission timing of the first uplinksignal outside the first repetition period.

According to another aspect, one or more of the objects are achieved bya method for an uplink transmission timing adjustment in a wirelesscommunication device served by a network node and configured to operatein a coverage enhancement mode. The coverage enhancement mode comprisesa repetitive transmission of a first uplink signal during a firstrepetition period. The method comprises determining a change in adownlink timing, determining whether the first repetition period isongoing and in response to the change in the downlink timing and thefirst repetition period being ongoing, performing an adjustment of anuplink transmission timing of the first uplink signal outside the firstrepetition period.

According to yet another aspect, one or more of the objects are achievedby a method for an uplink transmission timing adjustment in a wirelesscommunication device served by a network node and configured to operatein a coverage enhancement mode. The coverage enhancement mode comprisesrepetitive transmissions of multiple uplink signals within respectiverepetition periods. The method comprises aligning the respectiverepetition periods by shifting in time at least one of start or endpoints of the respective repetition periods according to a predeterminedrule, such that an overlap time of the respective repetition periods ismaximized or single transmission of the multiple uplink signals isminimized.

According to yet another aspect, one or more of the objects are achievedby a wireless communication device served by a network node andconfigured to operate in a coverage enhancement mode. The coverageenhancement mode comprises a repetitive transmission of a first uplinksignal during a first repetition period. The wireless communicationdevice comprises a first determining unit configured to determine achange in a downlink timing, a second determining unit configured todetermine whether the first repetition period is ongoing, and anadjusting unit configured to, in response to the change in the downlinktiming and the first repetition period being ongoing, perform anadjustment of an uplink transmission timing of the first uplink signaloutside the first repetition period.

According to yet another aspect, one or more of the objects are achievedby a method for enhancing an uplink transmission timing adjustmentprocedure for a wireless communication device. The method comprisesdetermining that the wireless communication device is to be configuredto transmit at least two uplink signals over at least partly overlappingrepetition periods, and enabling the wireless communication device toalign the respective repetition periods of the at least two uplinksignals.

According to yet another aspect, one or more of the objects are achievedby a network node for enhancing an uplink transmission timing adjustmentprocedure for a wireless communication device. The network nodecomprises a determining unit configured to determine that the wirelesscommunication device is to be configured to transmit at least two uplinksignals over at least partly overlapping repetition periods, and anenabling unit configured to enable the wireless communication device toalign the respective repetition periods of the at least two uplinksignals.

According to yet another aspect, one or more of the objects are achievedby a wireless communication device served by a network node andconfigured to operate in a coverage enhancement mode. The wirelesscommunication device comprises a non-transitory machine-readable storagemedium having stored instructions therein, and a processorcommunicatively coupled to the non-transitory machine-readable storagemedium. The processor is configured to execute the instructions storedin the non-transitory machine-readable storage medium to perform amethod in the wireless communication device.

According to yet another aspect, one or more of the objects are achievedby a network node for enhancing an uplink transmission timing adjustmentprocedure for a wireless communication device. The network nodecomprises a non-transitory machine-readable storage medium having storedinstructions therein, and a processor communicatively coupled to thenon-transitory machine-readable storage medium. The processor isconfigured to execute the instructions stored in the non-transitorymachine-readable storage medium to perform a method in the network node.

According to yet another aspect, one or more of the objects are achievedby a method in a UE served by a serving cell. The method comprises thesteps of determining that downlink timing of a reference signal receivedat the UE from the serving cell has changed with respect to a referencetime by a certain amount; determining whether the UE is configured totransmit a first uplink signal with a certain repetition over a timeperiod, T0; and determining an adjustment time resource in which theuplink transmit timing for transmitting the first signal is adjusted,which adjustment time resource is determined in response to thedetermined change in the downlink reception timing and depends onwhether the UE is configured with the first signal with or withoutrepetitions (e.g., adjustment time resource such as a subframe occursimmediately after T0 if repetition is configured).

According to yet another aspect, one or more of the objects are achievedby a method in a UE served by a serving cell. The method comprises thesteps of: determining that downlink timing of a reference signalreceived at the UE from the serving cell has changed with respect to areference time by a certain amount; determining that the UE isconfigured to transmit at least two uplink signals over at least partlyoverlapping repetition periods, comprising a first uplink signal with acertain repetition over a time period, T1 and a second uplink signalwith a certain repetition over a time period, T2; and determining anadjustment time resource in which the uplink transmit timing fortransmitting at least one of the first signal and the second signal isadjusted, which adjustment time resource is determined in response tothe determined change in the downlink reception timing and furtherdepends on the relations between the starting times of T1 and T2 and/orterminating times of T1 and T2 (e.g., adjustment time resource such as asubframe occurs immediately after T2 if T2 terminates after T1).

According to yet another aspect, one or more of the objects are achievedby a method in a network node serving a UE. The method comprises thesteps of: determining that downlink timing of a reference signalreceived at the UE from the serving cell has changed with respect to areference time by a certain amount; determining that the UE is to beconfigured to transmit at least two uplink signals over at least partlyoverlapping repetition periods comprising a first uplink signal with acertain repetition over a time period, T1 and a second uplink signalwith a certain repetition over a time period, T2; and configuring the UEwith information for enabling the UE to transmit the first uplink signaland the second uplink signal such that T1 and T2 are related by acertain relation, e.g., one or more of: T1 and T2 start at the sametime, e.g., in the same time resource such as in the same subframe, T1and T2 end at the same time, e.g., in the same time resource such as inthe same subframe, T1 and T2 start within a certain time duration (Δ 1),e.g., within X number of time resources such as 5 subframes, and T1 andT2 end within a certain time duration (Δ2), e.g., within Y number oftime resources such as 10 subframes.

According to yet another aspect, one or more of the objects are achievedby a computer-readable medium carrying instructions, which, whenexecuted by a processor, causes the processor to carry out one or moreof the above methods.

According to yet another aspect, one or more of the objects are achievedby a computer-program accessible by a processor of a wirelesscommunication device or a network node, which when executed by theprocessor, causes the processor to carry out one or more of the abovemethods.

One or more of these aspects can facilitate accumulation and filteringof repeated uplink transmissions at the network node side, and thusimprove the uplink throughput of the wireless communication system.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments in the disclosure may best be understood by referring to thefollowing description and the accompanying drawings that are used toillustrate embodiments of the disclosure. In the drawings:

FIG. 1 is a simplified block diagram of a wireless communication systemaccording to an exemplary embodiment;

FIG. 2a illustrates a method performed by a wireless communicationdevice for uplink transmission timing control, according to an exemplaryembodiment;

FIG. 2b illustrates a method performed by a wireless communicationdevice for uplink transmission timing control, according to anotherexemplary embodiment;

FIG. 3a is a simplified block diagram of a wireless communication deviceaccording to an exemplary embodiment;

FIG. 3b is a simplified block diagram of a wireless communication deviceaccording to another exemplary embodiment;

FIG. 4 illustrates a method performed by a network node for uplinktransmission timing control, according to an exemplary embodiment;

FIG. 5a is a simplified block diagram of a network node according to anexemplary embodiment; and

FIG. 5b is a simplified block diagram of a network node according toanother exemplary embodiment.

DESCRIPTION OF EMBODIMENTS

The foregoing and other objects, features, and advantages of theembodiments described herein will be apparent from the following moreparticular description of preferred embodiments as illustrated in theaccompanying drawings in which reference characters refer to the sameparts throughout the various views. The drawings are not necessarily toscale, and the dimensions of certain features may have been exaggeratedfor the sake of clarity. Emphasis is instead being placed uponillustrating the principles of the embodiments herein.

Unless defined otherwise, technical and scientific terms used hereinhave the same meaning as is commonly understood by one of ordinary skillin the art to which this disclosure belongs. Unless it is otherwiseclear from the context, the terms “first”, “second”, and the like, asused herein do not denote any order, quantity, or importance, but ratherare used to distinguish one element from another. Also, the terms “a”and “an” do not denote a limitation of quantity, but rather denote thepresence of at least one of the referenced items. The term “or” is meantto be inclusive and mean one, some, or all of the listed items. The useof “including”, “comprising” or “having” and variations thereof hereinare meant to encompass the items listed thereafter and equivalentsthereof as well as additional items. The terms “connected” and “coupled”are not restricted to physical or mechanical connections or couplings,and can include electrical connections or couplings, whether direct orindirect. Furthermore, the terms “circuit”, “circuitry”, “controller”,and “processor” may include either a single component or a plurality ofcomponents, which are either active and/or passive and are connected orotherwise coupled together to provide the described function.

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,”, etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

Bracketed text and blocks with dashed borders (e.g., large dashes, smalldashes, dot-dash, and dots) may be used herein to illustrate optionaloperations that add additional features to embodiments of thedisclosure. However, such notation should not be taken to mean thatthese are the only options or optional operations, and/or that blockswith solid borders are not optional in certain embodiments of thedisclosure.

In the following description and claims, the terms “coupled” and“connected”, along with their derivatives, may be used. It should beunderstood that these terms are not intended as synonyms for each other.“Coupled” is used to indicate that two or more elements, which may ormay not be in direct physical or electrical contact with each other,co-operate or interact with each other. “Connected” is used to indicatethe establishment of communication between two or more elements that arecoupled with each other.

eMTC

eMTC features specified in 3GPP technical contributions identified by3GPP as contribution documents 3GPP RP-152024 and 3GPP R1-157926 includea low-complexity user equipment (UE) category called UE category M1 (orCat-M1 for short) and coverage enhancement techniques, CE modes A and B,that can be used together with UE category M1 or any other LTE UEcategory.

All eMTC features, for both Cat-M1 and CE modes A and B, as defined in3GPP TS 36.133 V12.7.0, Section 7.1.2, operate using a reduced maximumchannel bandwidth compared to normal LTE. The maximum channel bandwidthin eMTC is 1.4 MHz, whereas it is up to 20 MHz in normal LTE. The eMTCUEs are still able to operate within the larger LTE system bandwidth,generally without problems. The main difference compared to normal LTEUEs is that the eMTCs can only be scheduled with 6 physical resourceblocks (PRBs) at a time, where each of these PRBs has a bandwidth of 180kHz.

In CE modes A and B, the coverage of physical channels is enhancedthrough various coverage enhancement techniques, the most importantbeing repetition or retransmission. In its simplest form, this meansthat the 1-millisecond subframe to be transmitted is repeated a numberof times, e.g., just a few times if a small coverage enhancement isneeded or hundreds or thousands of times if a large coverage enhancementis needed.

NB-IoT

The objective of the Narrow Band Internet-of-things (NB-IoT) initiativeof the 3GPP is to specify a radio access for cellular internet of things(IoT), based to a great extent on a non-backward-compatible variant ofE-UTRA (LTE), that addresses improved indoor coverage, support formassive number of low throughput devices, low delay sensitivity,ultra-low device cost, low device power consumption and (optimized)network architecture.

The NB-IoT carrier BW (Bw2) is 200 KHz. Examples of the operatingbandwidth (Bw1) of LTE, in contrast, are 1.4 MHz, 3 MHz, 5 MHz, 10 MHz,15 MHz, 20 MHz, etc.

NB-IoT radio access supports three different modes of operation:

-   -   1. ‘Stand-alone operation’ utilizing, for example, the spectrum        currently being used by GERAN systems as a replacement of one or        more GSM carriers. In principle this mode of operation can use        any carrier frequency which is neither within the carrier of        another co-located (or overlapping) system nor within the guard        band of another system's operating carrier. The other system can        be another NB-IoT operation or any other radio access technology        (RAT), e.g., LTE.    -   2. ‘Guard band operation’ utilizing the unused resource blocks        within a LTE carrier's guard-band. The term guard band may also        interchangeably be called guard bandwidth. As an example, in the        case of an LTE BW of 20 MHz (i.e., Bw1=20 MHz or 100 RBs), the        guard band operation of NB-IOT can be placed anywhere outside        the central 18 MHz but within 20 MHz LTE BW.    -   3. ‘In-band operation’ utilizing resource blocks within a normal        LTE carrier. The in-band operation may also interchangeably be        called in-bandwidth operation. More generally the operation of        one RAT within the BW of another RAT is also called in-band        operation. As an example, in a LTE BW of 50 RBs (i.e., Bw1 of 10        MHz or 50 RBs), NB-IoT operation over one resource block (RB)        within the 50 RBs is called in-band operation.

In NB-IoT, the downlink transmission is based on OrthogonalFrequency-Division Multiplexing (OFDM), with 15 kHz subcarrier spacingfor all the scenarios: standalone, guard-band, and in-band. For uplinktransmission, both multi-tone transmissions, based on single-carrierFrequency-Division Multiple Access (SC-FDMA), and single tonetransmission are supported. This means that the physical waveforms forNB-IoT in downlink and also partly in uplink are similar to those inlegacy LTE.

In the downlink design, NB-IoT supports both master informationbroadcast and system information broadcast which are carried bydifferent physical channels. For in-band operation, it is possible forNB-IoT UE to decode NB-PBCH (also referred to as NPBCH) without knowingthe legacy PRB index. NB-IoT supports both downlink physical controlchannel (NB-PDCCH, also referred to as NPDCCH) and downlink physicalshared channel (PDSCH, also referred to as NPDSCH). The operation modeof the NB-IoT radio access must be indicated to the UE, and currently3GPP consider indication by means of NB-SSS (also referred to as NSSS),NB-MIB (carried on NB-PBCH, also referred to as NPBCH), or perhaps otherdownlink signals.

The reference signals to be used in NB-IoT have not yet been specified.However, it is expected that the general design principle will followthat of legacy LTE. Downlink synchronization signals will most likelyconsist of primary synchronization signal (NB-PSS, also referred to asNPSS) and secondary synchronization signal (NB-SSS, also referred to asNSSS).

Half-Duplex Operation

In half-duplex (HD) operation, or more specifically half-duplex FDD(HD-FDD) operation, the uplink (UL) and downlink (DL) transmissions takeplace on different paired carrier frequencies but not simultaneously intime in the same cell. This means that the uplink and downlinktransmissions take place in different time resources. Examples of a timeresource are symbols, time slots, subframes, transmission time intervals(TTIs), interleaving times, etc. In other words, uplink and downlink(e.g., subframes) do not overlap in time. The number and location ofsubframes used for downlink, uplink, or unused subframes can vary on aframe-to-frame basis, or on a basis of multiple frames. For example, inone radio frame (say frame#1), subframes #9, #0, #4 and #5 may be usedfor downlink, while subframes #2 and #7 are used for uplinktransmission. But in another frame (say frame#2), subframes #0 and #5are used for downlink and subframes #2, #3, #5, #7 and #8 are used foruplink transmission.

Timing Advance

In order to preserve orthogonality in uplink SC-FDMA transmissions, theuplink transmissions from multiple user equipments (UEs) in LTE need tobe time aligned at a receiver, such as a base station, e.g., an LTEeNode B or the like. This means that the transmit timing of those UEsthat are under the control of the same eNode B should be adjusted toensure that their received signals arrive at the eNode B receiver atapproximately the same time. More specifically, their received signalsshould arrive well within the cyclic prefix (CP), where the normal CPlength is about 4.7 μs. This ensures that the eNode B receiver is ableto use the same resources, i.e., the same Discrete Fourier Transform(DFT) or Fast Fourier Transform (FFT) resource, to receive and processthe signals from multiple UEs.

The uplink timing advance (TA) is maintained by the eNode B throughtiming advance commands, also referred to as timing alignment commands,sent to the UE based on measurements on uplink transmissions from thatUE. For example, the eNode B measures a two-way propagation delay orround-trip time for each UE, to determine the value of the TA requiredfor that UE.

For a timing advance command received on subframe n, the correspondingadjustment of the uplink transmission timing is applied by the UE fromthe beginning of subframe n+6. The timing advance command indicates thechange of the uplink timing relative to the current uplink timing of theUE transmission as multiples of 16 Ts, where Ts=32.5 ns and is calledthe “basic time unit” in LTE.

In the case of random access response messages transmitted by the eNodeB's, an 11-bit timing advance command (TA) for a Timing Advance Group(TAG) indicates NTA values by index values of TA=0, 1, 2, . . . , 1282,where an amount of the time alignment for the TAG is given by NTA=TA×16.NTA is defined above in section “Alignment of E-UTRA TDD measurementgaps with particular subframe offsets”.

In other cases, a 6-bit timing advance command (TA) for a TAG indicatesadjustment of the current NTA value, NTA,old, to the new NTA value,NTA,new, by index values of TA=0, 1, 2, . . . , 63, whereNTA,new=NTA,old+(TA−31)×16. Here, adjustment of NTA value by a positiveor a negative amount indicates advancing or delaying the uplinktransmission timing for the TAG by a given amount respectively.

Timing advance updates are signaled by the evolved Node B (eNB) to theUE in MAC PDUs.

Coverage Enhancements

The path loss between IoT device and the base station can be very largein some scenarios, such as when the device is used as a sensor ormetering device located in a remote location such as in the basement ofthe building. In such scenarios, the reception of the signal from basestation may be very challenging. For example, the path loss can be worseby 20 dB, compared to normal operation. In order to cope with suchchallenges, the coverage in uplink and/or in downlink has to besubstantially enhanced with respect to the normal coverage (alsoreferred to as legacy coverage). This is realized by employing one orseveral advanced techniques in the UE and/or in the radio network nodefor enhancing the coverage. Some non-limiting examples of such advancedtechniques include transmit power boosting, repetition of transmittedsignal, applying additional redundancy to the transmitted signal, use ofadvanced/enhanced receiver architectures, etc. In general, whenemploying such coverage enhancing techniques, the IoT radio access isregarded to be operating in ‘coverage enhancing mode’ or coverageextending mode.

When coverage enhancement is provided by means of transmissionrepetitions, the maximum number of repetitions for PDSCH and PUSCH,respectively, for coverage enhancement modes A and B are given bycell-specific broadcasted parameters:

-   -   pdsch-maxNumRepetitionCEmodeA (up to 32 repetitions),    -   pdsch-maxNumRepetitionCEmodeB (up to 2048 repetitions),    -   pusch-maxNumRepetitionCEmodeA (up to 32 repetitions),    -   pusch-maxNumRepetitionCEmodeB (up to 2048 repetitions).

The exact number of repetitions to use by a particular wirelesscommunication device is signaled dynamically via the downlink controlinformation (DCI), which is carried over the downlink control channelM-PDCCH. This channel, too, may be repeated according to a specificrepetition number individually configured for each wirelesscommunication device:

-   -   mPDCCH-NumRepetition (up to 256 repetitions).        When the wireless communication device transmits on the uplink        control channel, it may use repetitions as individually        configured by the network node:    -   pucch-NumRepetitionCE-Format1 (up to 8 (mode A) or 32 (mode B)        repetitions),    -   pucch-NumRepetitionCE-Format2 (up to 8 (mode A) or 32 (mode B)        repetitions).        Hence, depending on the coverage, wireless communication devices        may apply different number of repetitions.

A low complexity UE (e.g., a UE with one receiver, or “Rx”) may also becapable of supporting enhanced coverage mode of operation. The coveragelevel of the UE with regard to a cell may be expressed in terms of asignal level, such as signal quality, signal strength or path loss, withregard to that cell.

An Example Wireless Communication System

FIG. 1 is a simplified block diagram of an exemplary wirelesscommunication system 100 in which one or more embodiments describedherein may be implemented. The wireless communication system 100 may bedescribed below with reference to LTE systems, and using LTEterminology. However, the techniques and apparatus described in thecontext of system 100 may be applicable, with suitable modifications, toany RAT or multi-RAT systems where the UE receives and/or transmitsignals (e.g., data), e.g., LTE FDD/TDD, WCDMA/HSPA, GSM/GERAN, Wi Fi,WLAN, CDMA2000, NR, etc. The network node could be configured foroperation using more than one cell, e.g., using PCell, SCell, PSCell.

In an example embodiment, the wireless communication system 100 mayinclude at least one network node 120 and at least one wirelesscommunication device 110 served by the network node 120. The number ofnetwork nodes 120 and/or the wireless communication devices 110 as shownin FIG. 1 is only illustrative, and not limiting. The network node 120may be referred to a radio base station, sometimes also referred to inthe art as a macro base station, a node B, or B-node, an eNodeB (eNB),and may be sometimes also referred to in the art as a micro/femto/picobase stations, a micro/femto/pico node B, or micro/femto/pico B-node, amicro/femto/pico eNodeB (eNB). Further, the network node 120 could alsobe any other device in the wireless network, such as a WLAN accesspoint, that could enable similar contributions to the D2D communicationsherein as an eNodeB does.

The wireless communication devices 110 may be served by cells, and thenumbers served by different cells need not be identical. The term“wireless communication device” as used herein may indicate all forms ofdevices enabled to communicate via a communication network, such asmobile telephones (“cellular” telephones) and laptops with mobiletermination, and thus can be, for example, portable, pocket, hand-helddevices, such as mobile phones, smart phones, personal digitalassistants (PDA); computer-included devices, such as desktops, laptops;vehicles, or other devices, such as meters, household appliances,medical appliances, multimedia devices, etc., which communicate voiceand/or data with a radio access network.

FIG. 3a is a simplified block diagram of a wireless communication device110 according to an exemplary embodiment. As shown in FIG. 3a , thewireless communication device 110 may comprise, but not be limited to,an adjusting unit 320, and first, second and third determining units320, 330 and 340 operatively coupled with each other.

FIG. 5a is a simplified block diagram of a network node 120 according toan exemplary embodiment. As shown in FIG. 5a , the network node 120 maycomprise, but not limited to, a determining unit 510, an enabling unit520 and a transmitting unit 530 operatively coupled with each other.

More details regarding the wireless communication system 100 may bedescribed in connection with FIGS. 1, 3 a and 5 a hereinafter.

In an embodiment, the network node 120 transmits a reference signal tothe wireless communication device 110 via the transmitting unit 530, andthe wireless communication device 110 may be configured to operate in anenhanced coverage mode comprising a repetitive transmission of an uplinksignal during a repetition period, and to determine a change in adownlink timing from the reference signal via the first determining unit310. For example, the wireless communication device 110 may determinethat downlink timing of the received reference signal from the servingcell has changed with respect to a reference time by a certain amount.The wireless communication device 110 may further be configured todetermine whether the repetition period is ongoing via the seconddetermining unit 330. In response to the change in the downlink timing,the wireless communication device 110 may be configured to perform anadjustment of an uplink transmission timing of the uplink signal outsidethe repetition period via the adjusting unit 320.

In another embodiment, the network node 120 may determine, via thedetermining unit 510, that the wireless communication device 110 is tobe configured to transmit at least two uplink signals with at leastpartly overlapped repetition periods comprising as a first uplink signalwith a certain repetition over a time period T1 and a second uplinksignal with a certain repetition over a time period T2, and thus enable,via the enabling unit 520, the wireless communication device 110 toalign the repetition periods T1 and T2 according to a predeterminedrule, such that an overlap time of the repetition periods T1 and T2 canbe maximized or single transmission of the at least two uplink signalscan be minimized.

For example, the network node 120 may configure the wirelesscommunication device 110 with information for enabling the wirelesscommunication device 110 to transmit the first uplink signal and thesecond uplink signal such that the repetition periods T1 and T2 arerelated by a certain relation, e.g., one or more of:

-   -   the repetition periods T1 and T2 start at the same time, e.g.,        in the same time resource, such as in the same subframe;    -   the repetition periods T1 and T2 end at the same time, e.g., in        the same time resource such as in the same subframe;    -   the repetition periods T1 and T2 start within a certain time        duration (Δ1), e.g., within X number of time resources such as 5        subframes; and    -   the repetition periods T1 and T2 end within a certain time        duration (Δ2), e.g., within Y number of time resources such as        10 subframes.

In an embodiment, the third determining unit 340 in the wirelesscommunication device 110 may be configured to determine whether therepetition period is longer than one radio resource time unit based onone of: downlink control information (DCI) transmitted by the networknode, wherein the DCI contains explicit or implicit information on anumber of repetitions to use for the repetitive transmission of thefirst uplink signals, and radio resource control (RRC) configurationprovided by the network node, wherein the RRC configuration contains anumber of resources for the wireless communication device in a radioresource time unit, and wherein the number of resources explicitly orimplicitly indicates the number of repetitions.

An Example Wireless Communication Device

The timing adjustment behavior of a wireless communication devicecompliant to the EUTRAN standard is governed by several rules specifiedin 3GPP 36.133 V12.9.0, section 7.1.2. According to these rules, fornon-initial transmission and LTE bandwidth 1.4 MHz (minimum sample rate1.92 MS/s):

-   -   the maximum timing adjustment in one correction shall not exceed        17.5 TS (0.6 μs),    -   the minimum aggregated adjustment rate shall be 7 TS (0.2 μs)        per second, and    -   the maximum aggregated adjustment rate shall be 17.5 TS (0.6 μs)        per 200 ms.        For initial transmission and LTE bandwidth 1.4 MHz (minimum        sample rate 1.92 MS/s):    -   initial transmission timing error shall be less than ±24*TS (0.8        μs)        By initial transmission the standard refers to the first        transmission in a DRX cycle of PUCCH, PUSCH, and SRS or a        transmission of PRACH. By non-initial transmission the standard        refers to transmissions following the initial transmission.

It is not specified in the standard whether a first transmission inHD-FDD uplink burst of repetitions is to be considered as an initialtransmission or not. Since the wireless communication device has notbeen in a DRX inactivity period prior to the onset of the uplinktransmission, and the HD-FDD uplink burst is not a transmission ofPRACH, the first transmission in an uplink burst may be considered anon-initial transmission. In such an implementation, any serving celltiming drift that has been detected during the downlink repetitionperiod of the HD-FDD would be corrected during the uplink repetitionperiod, and would be corrected gradually according to the existing rulesfor non-initial transmissions as summarized above.

Gradual uplink timing changes during an uplink repetition period may beparticularly challenging for the network node. The gradual timing changeresults in a gradual change of (linear) phase of the received signal,and hence changes the perceived radio channel. Accumulation or filteringof channel estimates over the time domain may result in distortedchannel estimates, and accumulation of the message part of the signalmay likewise lead to a distorted accumulated message. The distortion inturn results in a degraded decoder performance in the network node.

In eMTC operation in FDD or TDD configuration, where downlink and uplinkrepetition periods may overlap each other, the wireless communicationdevice may acquire new information on the downlink cell timing during anongoing uplink transmission burst. If the wireless communication devicechanges the uplink timing during the repetition period, the gradualchange in uplink timing will introduce distortion of the accumulated orfiltered signals on the network node receiver side as described above,with degraded decoder performance in the network node. One differencefrom the HD-FDD case is that it can be expected that the frequency driftof the wireless communication device is relatively small, since first,the device has more opportunities to synchronize with the downlinkcarrier, and secondly, the uplink transmission power amplifier (PA) isoperating during the time the UE synchronizes to the downlink carrier,leading to less fluctuations in temperature and hence a more stablefrequency reference from the crystal oscillator.

In NB-IoT radio access, it is foreseen that it will be sufficient to usea downlink sample rate of about 240 kS/s, since the NB-IoT downlinksystem bandwidth is limited to 200 kHz, i.e., considerably less than foreMTC. The lower sample rate potentially leads to more dramatic servingcell downlink timing adjustments, since a one sample adjustmentcorresponds to ±128 TS (±4.2 μs). For an adjustment of downlink timingof one sample length, it would take up 1.5 seconds (1500 uplink TTIs,derived from maximum change of 17.5 TSper 200 ms) to adapt the uplinktiming, if the existing solution from EUTRAN is used also for NB-IoT.During this time, the gradual changes in uplink transmit timing wouldlead to distortion as discussed above.

Clearly such uplink transmit timing control is not adequate for wirelesscommunication devices that are engaged in communication whererepetitions of uplink transmissions are used. The techniques andapparatus described herein address these issues, and include multipleembodiments for a wireless terminal, e.g., a UE, configured fortransmitting signals in the uplink with certain number of repetitions.The term signal herein may refer to any of:

-   -   a physical signal. A physical signal does not contain higher        layer information. Examples of uplink physical signals are SRS,        DMRS, any type of reference signal, etc.    -   a physical channel. A physical channel contains higher layer        information, e.g., RRC message, data, MAC, scheduling        information, HARQ information, measurement results like CSI,        etc. Examples of uplink physical channels are PUCCH, M-PUCCH,        NB-IoT PUCCH (a.k.a. NPUCCH), PUSCH, NB-IoT PUSCH (a.k.a        NPUSCH), PRACH, NB-PRACH (a.k.a. NPRACH), any type of uplink        control or data channel, etc.

FIG. 2a illustrates a method 200, performed by a wireless communicationdevice 110, for uplink transmission timing control adjustment accordingto an exemplary embodiment, where the wireless communication device 110is served by the network node 120 and configured to operate in acoverage enhancement mode comprising a repetitive transmission of anuplink signal within a repetition period.

In an embodiment, the wireless communication device 110 is served by thenetwork node 120 and may be configured to operate in a coverageenhancement mode, where the coverage enhancement mode comprises arepetitive transmission of an uplink signal during a repetition period.In this embodiment, the first determining unit 310 may be configured todetermine a change in a downlink timing of the network node 120, and theadjusting unit 330 may be configured to, in response to the change inthe downlink timing and the repetition period being ongoing, perform anadjustment of an uplink transmission timing outside the ongoingrepetition period.

More details regarding the wireless communication device 110 may bedescribed in connection with FIGS. 2a and 3a hereinafter.

As shown in FIG. 2a , the first determining unit 310 may be configuredto determine that the downlink timing of the serving cell or the networknode 120 has changed, at step 210, and the third determining unit 340may be configured to check or determine whether uplink repetitions ofrepetition factor R larger than 1 are configured by the network node120, at step 220. If no such repetitions are configured, the uplinktransmission timing may be gradually adjusted according to the legacyrules on gradual adjustment, such as rules specified in 3GPP TS 36.133V12.7.0, Section 7.1.2, at step 230.

For example, the rules may comprise one or more of the conditionsconsisting of:

-   -   a. the maximum amount of the magnitude of the timing change in        one adjustment shall be Tq seconds,    -   b. the minimum aggregate adjustment rate shall be 7*Ts per        second, and    -   c. the maximum aggregate adjustment rate shall be Tq per 200 ms,    -   d. where Tq is depending on downlink and uplink characteristics        and is mapped on the downlink bandwidth, e.g., as in Table 1        below.

TABLE 1 Te Timing Error Limit Downlink Bandwidth (MHz) Te 1.4 24 × Ts ≧312 × Ts Note: Ts is the basic timing unit defined 3GPP TS 36.211

The downlink characteristics comprise any or a combination of: downlinksystem bandwidth, and coverage enhancement mode of operation, e.g., ModeA or Mode B operation, or an operation of repetitions. The uplinkcharacteristics may comprise any or a combination of: uplink systembandwidth, subcarrier distance or spacing, symbol length and cyclicprefix length.

If, on the other hand, the third determining unit 340 determines thatuplink repetitions are configured, the second determining unit 330 maybe configured to check whether it is currently engaged in an uplinktransmission where messages are repeated, at step 240. If not, theadjusting unit 320 may be configured to fully adjust the uplinktransmission timing substantially immediately in response to the changeddownlink timing in the cell or the network node 120, at step 250.

For example, in response to a change in the downlink timing and therepetition period being not ongoing, the uplink transmission timing maybe adjusted to within ±Te seconds before the uplink repetition periodbegins, and shall remain constant during the next uplink repetitionperiod, where Te is depending on the above downlink and uplinkcharacteristics, and the uplink transmission timing shall remainconstant during the uplink repetition period.

If, on the other hand, the second determining unit 330 determines thatthe wireless communication device 110 is engaged in an uplinktransmission, the adjusting unit 320 may be configured to postpone theuplink transmission timing adjustment until the current uplinktransmission period has ended, and preferably substantially immediatelythereafter, to be prepared for the next uplink transmission as early aspossible, at step 260.

For example, in response to a change in the downlink timing and therepetition period being ongoing, the uplink transmission timing may beadjusted to within ±Te seconds before the next uplink repetition periodor next uplink transmission begins and after the ongoing uplinktransmission period has ended, and shall remain constant during the nextongoing uplink repetition period, where Te is depending on the abovedownlink and uplink characteristics.

At step 210, the first determining unit 310 may be further configured todetermine a change in a downlink timing of a reference signal receivedat the wireless communication device from the network node with respectto a reference time. For example, the first determining unit 310 may befurther configured to determine a relative change of timing of one ormore reference signals broadcasted by the network node on the downlink,to a timing predicted for the reference signals by the wirelesscommunication device based on one or more previous reference signals.

At step 220, the third determining unit 340 may be further configured tocheck whether a repetition period is longer than one radio resource timeunit, based on DCI transmitted by the network node, where the DCIcontains explicit or implicit information on the number of repetitionsto use for a granted uplink transmission, e.g., applicable for PUSCH,depending on DCI and maxRepetitions. Besides, this checking step may bebased on RRC configuration provided by the network node, where the RRCconfiguration contains the number of resources for the wirelesscommunication device in a radio resource time unit, and where saidnumber of resources explicitly or implicitly indicates the number ofrepetitions, e.g., applicable for PUCCH, depending on #RBs andmaxRepetitions. One radio resource time unit may correspond to oneEUTRAN subframe (1 ms), e.g., applicable for eMTC, or to two EUTRANsubframes (2 ms), e.g., applicable for NB-IoT3.75 kHz option.

An Example Method in a UE Configured to Transmit One Signal withRepetition

The presently disclosed techniques include methods implemented in awireless communication device 110, such as UE, which is served by thenetwork node and is configured to transmit one uplink signal withrepetition during a repetition period. These methods may include, forexample, the steps of: determining, by the first determining unit 310, achange in a downlink timing of the network node, 210; and in response tothe change in the downlink timing and the ongoing repetition period,performing, by the adjusting unit 320, an adjustment of an uplinktransmission timing outside the ongoing repetition period, 260. Themethod may further comprise the steps of: determining whether the UE isconfigured to transmit a first uplink signal with a certain repetitionover a time period, T0; determining an adjustment time resource in whichthe uplink transmit timing for transmitting the first signal isadjusted, which adjustment time resource is determined in response tothe determined change in the downlink reception timing and depends onwhether the UE is configured with the first signal with or withoutrepetitions (e.g., adjustment time resource such as a subframe occursimmediately after T0 if repetition is configured).

These example methods concern a new UE behavior in terms of UE transmittiming adjustment. A UE that is configured to transmit any of variousuplink signals (e.g., PRACH, SRS, PUSCH, M-PUCCH, NB-PUSCH, NB-PUCCH,etc) on the uplink using a repetition factor R that is larger than one,i.e., R>1, shall consider the onset of each separate repetition periodto be an initial transmission. Moreover, in the cases of FDD or TDD modeof operation, the UE shall not, when R>1, carry out autonomous changesof the uplink timing during the current repetition burst, i.e., uplinktransmission period or duration over which an uplink signal beingtransmitted is repeated.

This new UE behavior is needed because when message repetition is usedit is undesirable to have the UE changing the uplink transmit timingduring the repetition period. Any change in the UE uplink timing maydestroy the channel estimation at the base station receiver. This inturn will prevent the base station receiver from receiving or correctlyreceiving signals transmitted by the UE with repetition.

In this embodiment, it is assumed that the UE is configured to transmitone signal with repetition over the entire repetition period (T0). Forexample, the UE can be configured to transmit only PUSCH with 32repetitions over 32 consecutive uplink time resources, e.g., 32subframes, 32 TTIs, 32 interleaving time periods, etc. This correspondsto a repetition period (T0) of 32 ms for FDD. However, T0 in case ofHD-FDD and TDD will be longer than 32 milliseconds (ms); the actualvalue of T0 would depend on the number of uplink subframes available ina frame.

By handling each uplink repetition period as an initial transmission,and not allowing UE-autonomous uplink timing corrections during anongoing uplink repetition period, distortion on the network nodereceiver side can be reduced.

An Example Method in a UE Configured to Transmit Signals Both with andwithout Repetitions

The presently disclosed techniques include methods implemented in awireless communication device, such as UE, for adjusting uplink timingwhen configured to transmit combination of signals with and withoutrepetitions during a repetition period. In these methods, the UE isconfigured to operate in a coverage enhancement mode comprising arepetitive transmission of a first uplink signal during a firstrepetition period and a transmission of a second uplink signal without arepetition. These methods include determining, e.g., by the firstdetermining unit 310, a change in a downlink timing of the servingnetwork node or cell, at step 210, and in response to the change in thedownlink timing and the ongoing repetition period, performing, e.g., bythe adjusting unit 320, an adjustment of an uplink transmission timingof the first uplink signal outside the first repetition period, at step260. The step of performing may further configure the second uplinksignal with the same uplink transmission timing as that of the firstuplink signal.

In these methods, it is assumed that the UE is configured to transmit atleast one first signal with repetition over a repetition period (T0) andalso another second signal during the repetition period of the firstsignal, i.e., during T0. For example, the UE can be configured totransmit PUSCH with 32 repetitions over T0 and the UE may also performat least one random access transmission during T0. It is assumed thatthe UE performs RA during T0 with one transmission attempt, i.e., anoriginal transmission only, without repetitions.

The UE may initiate a RA transmission autonomously or in response to arequest received from the network node. The UE may perform a RAtransmission for one or more of the following reasons, e.g., forperforming or enabling eNB to perform positioning measurement such asTA, UE Rx-Tx time difference, eNB Rx-Tx time difference, etc. Thus, a RAtransmission can, in principle, occur at any time uncorrelated with thefirst signal.

According to some embodiments, the UE is not allowed to perform anyautonomous uplink timing corrections even when transmitting the secondsignal during an ongoing uplink repetition period, T0 of the firstsignal. On the other hand, the UE may adjust its timing autonomously atthe start or at the end of the current repetition period of the firstsignal. More specifically, the UE may transmit the RA during T0 usingthe same timing which is being used for transmitting PUSCH. This timingwas the most favorable at the start of T0.

This corresponds to a repetition period (T0) of 32 ms for FDD. However,T0 in case of HD-FDD and TDD will be longer than 32 ms; the actual valueof T0 would depend on the number of uplink subframes available in aframe.

An Example Method in a UE Configured to Transmit Multiple Signals withRepetitions, During Overlapping Repetition Periods

The presently disclosed techniques include methods implemented in awireless communication device 100, such as a UE, of adjusting uplinktiming when the wireless communication device 100 is configured totransmit multiple signals with repetitions during overlapping repetitionperiods. For example, the UE may be configured to operate in a coverageenhancement mode comprising repetitive transmissions of at least twouplink signals with at least partly overlapping repetition periodscomprising a first uplink signal with a certain repetition over a timeperiod T1 and a second uplink signal with a certain repetition over atime period T2.

These methods may comprise: determining, by the first determining unit310, a change in a downlink timing of the serving network node or cell,at step 210, and in response to the change in the downlink timing andthe ongoing repetition period(s), performing, by the adjusting unit 320,uplink transmission timings outside both of the first and secondrepetition periods, at step 260. The methods may further comprise a stepof determining an adjustment time resource in which the uplink transmittiming for transmitting at least one of the first signal and the secondsignal is adjusted, which adjustment time resource is determined inresponse to the determined change in the downlink reception timing andfurther depends on the relations between the starting times of T1 and T2and/or terminating times of T1 and T2 (e.g., an adjustment time resourcesuch as a subframe occurs immediately after T2, if T2 terminates afterT1).

In these embodiments, it is assumed that the UE is configured totransmit at least one first signal with a certain repetition over afirst repetition period T1 and at least a second signal with a certainrepetition over a second repetition period T2. It is further assumedthat T1 and T2 at least partly overlap. For example, the UE can beconfigured to transmit a first signal, such as PUSCH, with 32repetitions over T1. The UE may also be configured to transmit a secondsignal, such as a random access, with a certain number of repetitionsduring T2. In yet another scenario it is assumed that the UE performs RAduring T0 with one transmission attempt, i.e., original transmissiononly without repetitions (R=1).

As noted above, a UE may initiate RA transmission autonomously or inresponse to a request received from the network node. The UE may performRA transmission for one or more of the following reasons, e.g., forperforming or enabling eNB to perform positioning measurement such asTA, UE Rx-Tx time difference, eNB Rx-Tx time difference, etc.

According to these embodiment of the disclosed method the UE behaviorcan be further described as follows. The UE is not allowed to performany autonomous uplink transmit timing corrections or adjustments duringongoing uplink repetition periods of any of the uplink signals but isallowed to autonomously adjust its uplink transmit timing when norepetition period is ongoing, such as: before the beginning of therepetition period of a signal with the earliest starting time comparedto the starting times of repetition periods of other signals overlappingin time, or after the end of the repetition period of a signal with thelatest terminating time compared to the terminating times of repetitionperiods of other signals overlapping in time.

The above UE behavior is elaborated with the example comprising thefirst and second signal transmission with at least partly overlappingrepetition periods of T1 and T2 respectively. Assume that T1 startsbefore T2 and T1 ends before T2, i.e., T2 terminates after T1. In thisembodiment, the UE is not allowed to autonomously adjust its uplinktiming from the start of T1 and until the end of T2. However, the UE isallowed to autonomously adjust or change its uplink transmit timing justbefore T1 or just after T2.

An Example Method in a UE of Configuring Uplink Signals with Repetitionsto Enhance UE Uplink Timing Adjustment Procedures

FIG. 2b illustrates a method 280 performed by a wireless communicationdevice 110 for uplink transmission timing control, according to otherexemplary embodiments of the presently disclosed techniques. The method280 may be implemented in a UE (e.g., involving a RA transmission,etc.). In this method, the wireless communication device 110 is servedby a network node 120 and configured to operate in a coverageenhancement mode, wherein the coverage enhancement mode comprisesrepetitive transmissions of multiple uplink signals with respectiverepetition periods.

As shown in FIG. 2b , the method 280 may comprise aligning therespective repetition periods by shifting in time at least one of startor end points of the respective repetition periods according to apredetermined rule, such that an overlap time of the respectiverepetition periods is maximized or single transmission of the multipleuplink signals is minimized, at step 290.

The predetermined rule comprises one of:

-   -   a. the respective repetition periods to start at the same time;    -   b. the respective repetition periods to end at the same time;    -   c. the respective repetition periods to start within a first        time duration (Δ1), e.g., within a number of X time resources        such as 5 subframes; and    -   e. the respective repetition periods to end within a second time        duration Δ2), e.g., within a number of Y time resources such as        10 subframes.        The above relations between the repetition periods can be        implementation specific, pre-defined or configured at the UE by        the network node.

For example, assume that the UE is configured by the network node totransmit the first signal, PUSCH, with a certain repetition over therepetition period of T1. During T1, the network node may further requestthe UE to transmit a second signal, such as a random access, with acertain repetition over the repetition period of T2. As a special case,the repetition for the second signal may be 1, i.e., R=1. In an exampleimplementation, the UE may be configured to transmit RA with allrepetitions by the end of T1, i.e., T2 ends in the single and last timeresource just before or after the T1. By scheduling T2 at the end of T1,the UE is allowed to adjust its uplink transmit timing immediately afterT1, or one time resource after T1. In other words, the UE transmittiming adjustment is not delayed or the adjustment is applied withminimal delay when there are two or more signals configured for uplinktransmissions with overlapping repetition periods. In another example,the transmission during T1 has precedence over the transmission in T2,and since T2 extends over the remaining time of T1, the UE can correctthe timing at the start of T1. However, the UE would not be allowed tocorrect the timing at the onset of T2, since there would be a part of T1left after T2 had been started.

The aim of this approach is to allow alignment between the repetitionperiods of multiple uplink signals as much as possible. This alignmentenables the UE to adjust the uplink transmit timing immediately or witha shorter delay after the end of the repetition period of each uplinksignal. In other words, the overlap time of the repetition periods (Ta,Tb) is maximized, or single transmission of uplink signals is minimized.

FIG. 3b is a simplified block diagram of a wireless communication device110 that may be configured to carry out one or more of the techniquesdescribed herein. As shown in FIG. 3b , the wireless communicationdevice 110 may comprise, but is not limited to, an Input/OutputInterface 370, processor(s) 360, and a memory 350, operatively coupledwith each other.

The memory 350 may comprise, but not be limited to, a volatile (e.g.,RAM) and/or non-volatile memory (e.g., a hard disk or flash memory). Inan embodiment, the memory 350 may be configured to store a computerprogram, which when executed by the processor(s) 360, causes to theprocessor 360 to perform any method performed in the wirelesscommunication device 110. The combination of processor(s) 360 with sucha memory 350 may be referred to as a processing circuit; it will beappreciated that when the memory 350 stores a computer program forcarrying out one or more of the techniques described herein, theprocessing circuit is thereby configured to carry out those one or moretechniques. In some embodiments, the computer program can be stored in aremote location, for example computer program product 380, and beaccessible by the processor(s) 360 via, for example carrier 390.

The computer program product 380 can be distributed and/or stored on aremovable computer readable media, e.g., diskette, CD (Compact Disk),DVD (Digital Video Disk), flash or similar removable memory media (e.g.,compact flash, SD secure digital, memory stick, miniSD, MMC multimediacard, smart media), HD-DVD (High Definition DVD), or Bluray DVD, USB(Universal Serial Bus) based removable memory media, magnetic tapemedia, optical storage media, magneto-optical media, bubble memory, ordistributed as a propagated signal via a network (e.g., Ethernet, ATM,ISDN, PSTN, X.25, Internet, Local Area Network (LAN), or similarnetworks capable of transporting data packets to the infrastructurenode).

Network Node Side

FIG. 4 illustrates an example method 400 performed on the network sideof the wireless communication system, such as in a network node 120, acloud, or the like, for uplink transmission timing control, according toan exemplary embodiment. The network node 120, for example, may beconfigured to enhance an uplink transmission timing adjustment procedurefor a wireless communication device 110 served by the network node 120.As shown in FIG. 5a , the network node 120 may comprise, but not limitedto, a determining unit 510, an enabling unit 520 and a transmitting unit530.

In an embodiment, the determining unit 510 may be configured todetermine that the wireless communication device 110 is to be configuredto transmit at least two uplink signals over at least partly overlappingrepetition periods. The enabling unit 520 may be configured to enablethe wireless communication device 110 to align the respective repetitionperiods of the at least two uplink signals. More details regarding thenetwork node 120 may be described in connection with FIGS. 4, 5 a and 5b hereinafter.

As shown in FIG. 4, a method 400 for enhancing an uplink transmissiontiming adjustment procedure for a wireless communication device 110 maycomprise the steps of: determining, by the determining unit 510, thatthe wireless communication device 100 is to be configured to transmit atleast two uplink signals over at least partly overlapping repetitionperiods, e.g., as shown at step 410 of FIG. 4; and enabling, by theenabling unit 520, the wireless communication device 110 to align therespective repetition periods of the at least two uplink signals, asshown at step 420 of FIG. 4.

At step 420, the enabling unit 520 may be further configured to enablethe wireless communication device 110 to align the respective repetitionperiods by shifting in time at least one of the start or end points ofthe respective repetition periods according to a predetermined rule,such that an overlap time of the respective repetition periods ismaximized or single transmission of the multiple uplink signals isminimized. The predetermined rule comprises one of:

-   -   a. the respective repetition periods to start at the same time;    -   b. the respective repetition periods to end at the same time;    -   c. the respective repetition periods to start within a first        time duration (Δ1), e.g., within a number of X time resources        such as 5 subframes; and    -   d. the respective repetition periods to end within a second time        duration (Δ2), e.g., within a number of Y time resources such as        10 subframes.        The above relations between the repetition periods can be        implementation specific, pre-defined or configured at the UE by        the network node.

For example, assume that the UE is configured by the network node totransmit the first signal, PUSCH, with a certain repetition over therepetition period of T1. During T1 the network node may further requestthe UE to transmit a second signal, random access, with a certainrepetition over the repetition period of T2. As a special case, therepetition for the second signal may be 1, i.e., R=1. In one exampleimplementation, the UE may be configured to transmit RA with allrepetitions by the end of T1, i.e., T2 ends in the single and last timeresource just before or after the T1. By scheduling T2 at the end of T1,the UE is allowed to adjust its uplink transmit timing immediately afterT1, or one time resource after T1. In other words, the UE transmittiming adjustment is not delayed or the adjustment is applied withminimal delay when there are two or more signals configured for uplinktransmissions with overlapping repetition periods. In other embodiments,the transmission during T1 has precedence over the transmission in T2,and since T2 extends over the remaining time of T1, the UE can correctthe timing at the start of T1. However, the UE would not be allowed tocorrect the timing at the onset of T2, since there would be a part of T1left after T2 had been started.

The aim of this approach is to allow alignment between the repetitionperiods of multiple uplink signals as much as possible. This alignmentenables the UE to adjust the uplink transmit timing immediately or witha shorter delay after the end of the repetition period of each uplinksignal. In other words, the overlap time of the repetition periods (Ta,Tb) is maximized or single transmission of uplink signals is minimized.

FIG. 5b is a simplified block diagram of an example network node 120,which may be configured to carry out one or more of the techniquesdescribed herein. As shown in FIG. 5b , the network node 120 maycomprise, but is limited to, an Input/Output Interface 570, processor(s)560, and a memory 550, operatively coupled with each other.

The memory 550 may comprise, but not be limited to, a volatile (e.g.,RAM) and/or non-volatile memory (e.g., a hard disk or flash memory). Inan embodiment, the memory 550 may be configured to store a computerprogram, which when executed by the processor(s) 560, causes theprocessor(s) 560 to perform any method performed in the network node120. The combination of processor(s) 560 with such a memory 550 may bereferred to as a processing circuit; it will be appreciated that whenthe memory 550 stores a computer program for carrying out one or more ofthe techniques described herein, the processing circuit is therebyconfigured to carry out those one or more techniques. In someembodiments, the computer program can be stored in a remote location,for example computer program product 580, and be accessible by theprocessor 560 via, for example carrier 590.

The computer program product 580 can be distributed and/or stored on aremovable computer readable media, e.g., diskette, CD (Compact Disk),DVD (Digital Video Disk), flash or similar removable memory media (e.g.,compact flash, SD secure digital, memory stick, miniSD, MMC multimediacard, smart media), HD-DVD (High Definition DVD), or Bluray DVD, USB(Universal Serial Bus) based removable memory media, magnetic tapemedia, optical storage media, magneto-optical media, bubble memory, ordistributed as a propagated signal via a network (e.g., Ethernet, ATM,ISDN, PSTN, X.25, Internet, Local Area Network (LAN), or similarnetworks capable of transporting data packets to the infrastructurenode).

Although the method disclosed in this specification is exemplified forthe case when the communication takes place between a network node and aUE, the same method could also be applied when the communication occursbetween at least two nodes, node 1 and node 2.

Examples of the first node are NodeB, MeNB, SeNB, a network nodebelonging to MCG or SCG, base station (BS), multi-standard radio (MSR)radio node such as MSR BS, eNodeB, network controller, radio networkcontroller (RNC), base station controller (BSC), relay, donor nodecontrolling relay, base transceiver station (BTS), access point (AP),transmission points, transmission nodes, RRU, RRH, nodes in distributedantenna system (DAS), core network node (e.g., MSC, MME etc), O&M, OSS,SON, positioning node (e.g., E-SMLC), MDT, etc.

Examples of the second node are target device, device to device (D2D)UE, proximity capable UE (also referred to as ProSe UE), machine-type UEor UE capable of machine to machine (M2M) communication, PDA, PAD,Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE),laptop mounted equipment (LME), USB dongles, etc.

In case of ProSe (also known as D2D, sidelink) operation, thecommunication takes place between two ProSe capable UEs. The ProSeoperation by a UE is in a half-duplex mode, i.e., the UE can eithertransmit ProSe signals/channels or receive ProSe signals/channels. TheProSe UEs can also act as ProSe relay UEs whose tasks are to relay somesignals between ProSe UEs, but also to other nodes (e.g., network node).There is also associated control information for ProSe, some of which istransmitted by ProSe UEs and the other is transmitted by eNBs (e.g.,ProSe resource grants for ProSe communication transmitted via cellulardownlink control channels). The ProSe transmissions may occur onresources which are configured by the network or selected autonomouslyby the ProSe UE. The ProSe transmissions (e.g., PSDCH) include several(e.g., 3) retransmissions that are transmitted on consecutive subframes.The retransmissions or repetitions are needed to achieve good SD-RSRPmeasurement performance. The SD-RSRP measurement is used to performProSe relay selection by ProSe UEs.

In the foregoing specification, embodiments of the disclosure have beendescribed with reference to specific exemplary embodiments thereof. Itwill be evident that various modifications may be made thereto withoutdeparting from the broader spirit and scope of the disclosure as setforth in the following claims. The specification and drawings are,accordingly, to be regarded in an illustrative sense rather than arestrictive sense.

Throughout the description, embodiments of the present disclosure havebeen presented through flow diagrams. It will be appreciated that theorder of transactions and transactions described in these flow diagramsare only intended for illustrative purposes and not intended as alimitation of the present disclosure. One having ordinary skill in theart would recognize that variations can be made to the flow diagramswithout departing from the broader spirit and scope of the disclosure asset forth in the following claims.

Abbreviations Explanation

-   BW Bandwidth-   CE Coverage enhancement-   CP Cyclic prefix-   DCI Downlink control information-   DFT Discrete Fourier transform-   DMRS Demodulation reference signal-   DRX Discontinuous reception-   eMTC Evolved MTC-   EUTRA(N) Evolved universal terrestrial radio access (network)-   FDD Frequency division duplex-   GERAN GSM EDGE radio access network-   GSM Global system for mobile communication-   HARQ Hybrid automatic repeat request-   HD-FDD Half-duplex FDD-   IoT Internet of things-   kS/s kilo-samples per second-   LTE Long term evolution of UMTS-   MAC Media access control-   MIB Master information block-   M-PDCCH Machine-type PDCCH-   MTC Machine-type communication-   NB-IoT Narrowband IoT-   NB-MIB Narrowband MIB-   NB-M-PDCCH Narrowband M-PDCCH-   NB-PBCH Narrowband PBCH-   NB-PDCCH Narrowband PDCCH-   NB-PDSCH Narrowband PDSCH-   NB-PSS Narrowband PSS-   NB-SSS Narrowband SSS-   NB-PUCCH Narrowband PUCCH-   NB-PUSCH Narrowband PUSCH-   NTA Non-time alignment-   OFDM Orthogonal frequency division multiplexing-   PA Power amplifier-   PBCH Physical broadcast channel-   PDCCH Physical downlink control channel-   PDSCH Physical downlink shared channel-   PRACH Physical random access channel-   PRB Physical resource block-   PSS Primary synchronization signal-   PUCCH Physical uplink control channel-   PUSCH Physical uplink shared channel-   RA Random access-   RRC Radio resource control-   Rx Receive(r)-   SRS Sounding reference signal-   SSS Secondary synchronization signal-   TA Timing advance-   TAC Timing advance command-   TAG Timing advance group-   TDD Time division duplex-   Tx Transmit(ter)-   TTI Transmission time interval-   UE User equipment-   UL Uplink

1. A wireless communication system comprising: a wireless communicationdevice configured to operate in a coverage enhancement mode comprising arepetitive transmission of a first uplink signal during a firstrepetition period; and a network node serving the wireless communicationdevice, the network node comprising a transmitter configured to transmita reference signal to the wireless communication device, wherein thewireless communication device comprises a processing circuit configuredto: determine a change in a downlink timing based on the referencesignal; determine whether the first repetition period is ongoing; and,in response to the change in the downlink timing and the firstrepetition period being ongoing, perform an adjustment of an uplinktransmission timing outside the first repetition period.
 2. The wirelesscommunication system of claim 1, wherein the network node comprises aprocessing circuit configured to: determine that the wirelesscommunication device to be configured to transmit a second uplink signalduring a second repetition period at least partly overlapping the firstrepetition period; and enable the wireless communication device to alignthe first repetition period and the second repetition period accordingto a predetermined rule, such that an overlap time of the firstrepetition period and the second repetition period is maximized orsingle transmission of the multiple uplink signals is minimized.
 3. Thewireless communication system of claim 2, wherein the predetermined rulecomprises one of: the first repetition period and the second repetitionperiod to start at a same time; the first repetition period and thesecond repetition period to end at a same time; the first repetitionperiod and the second repetition period to start within a first timeduration; and the first repetition period and the second repetitionperiod to end within a second time duration.
 4. The wirelesscommunication system of claim 1, where the processing circuit of thewireless communication device is configured to determine whether thefirst repetition period is longer than one radio resource time unit,based on one of: downlink control information (DCI) transmitted by thenetwork node, wherein the DCI contains explicit or implicit informationon a number of repetitions to use for the repetitive transmission of thefirst uplink signals, and radio resource control (RRC) configurationprovided by the network node, wherein the RRC configuration contains anumber of resources for the wireless communication device in a radioresource time unit, and wherein the number of resources explicitly orimplicitly indicates the number of repetitions.
 5. A method for anuplink transmission timing adjustment in a wireless communication deviceserved by a network node and configured to operate in a coverageenhancement mode, wherein the coverage enhancement mode comprises arepetitive transmission of a first uplink signal during a firstrepetition period, the method comprising: determining a change in adownlink timing; determining whether the first repetition period isongoing; and in response to the change in the downlink timing and thefirst repetition period being ongoing, performing an adjustment of anuplink transmission timing outside the first repetition period.
 6. Themethod of claim 5, wherein determining a change in a downlink timingcomprises: determining a change in a downlink timing of a referencesignal received at the wireless communication device from the networknode with respect to a reference time.
 7. The method of claim 6, whereindetermining a change in a downlink timing comprises: determining arelative change of timing of one or more reference signals broadcastedby the network node on the downlink, to a timing predicted for thereference signals by the wireless communication device based on one ormore previous reference signals.
 8. The method of claim 5, wherein theuplink transmission timing is adjusted to within ±Te seconds before anext uplink transmission begins and after the ongoing uplinktransmission period has ended, and wherein Te is indicative of a timingerror limit value and depends upon downlink and uplink characteristics.9. The method of claim 5, wherein the coverage enhancement mode furthercomprises a transmission of a second uplink signal without a repetition,and wherein the step of performing further comprises: configuring thesecond uplink signal with a same uplink transmission timing as that ofthe first uplink signal.
 10. The method of claim 5, wherein the coverageenhancement mode further comprises a repetitive transmission of a seconduplink signal with a second repetition period at least partly overlappedwith the first repetition period, and wherein the step of performingfurther comprises: in response to the change in the downlink timing,performing the adjustment of the uplink transmission timing outside bothof the first and second repetition periods.
 11. The method of claim 5,wherein if the first repetition period is not ongoing, the uplinktransmission timing is adjusted to within ±Te seconds before the firstrepetition period begins, and wherein Te is indicative of a timing errorlimit value and depends upon downlink and uplink characteristics. 12.The method of claim 8, wherein the uplink characteristics comprises anyor a combination of uplink system bandwidth, subcarrier distance, symbollength, cyclic prefix length, and wherein the downlink characteristicscomprises any or a combination of downlink system bandwidth, and anoperation mode of repetition.
 13. The method of claim 5, furthercomprising determining whether the first repetition period is longerthan one radio resource time unit, based on one of: downlink controlinformation (DCI) transmitted by the network node, wherein the DCIcontains explicit or implicit information on a number of repetitions touse for the repetitive transmission of the first uplink signals, andradio resource control (RRC) configuration provided by the network node,wherein the RRC configuration contains a number of resources for thewireless communication device in a radio resource time unit, and whereinthe number of resources explicitly or implicitly indicates the number ofrepetitions.
 14. The method of claim 13, wherein if the first repetitionperiod is not longer than one radio resource time unit, the uplinktransmission timing is adjusted according to a rule comprising thefollowing conditions: a. a maximum amount of a magnitude of a timingchange in one adjustment shall be Tq seconds; b. a minimum aggregateadjustment rate shall be 7*Ts per second, wherein Ts is a basic timingunit; and c. the maximum aggregate adjustment rate shall be Tq per 200ms, wherein Tq is depending on downlink and uplink characteristics. 15.The method of claim 14, wherein Tq is mapped on a downlink bandwidthaccording to a table of: Downlink Bandwidth (MHz) Tq 1.4 17.5 Ts  3 9.5Ts 5 5.5 Ts ≧10 3.5 Ts


16. The method of claim 13, wherein the one radio resource time unitcorresponds to one Evolved universal terrestrial radio access network(EUTRAN) subframe or two EUTRAN subframes.
 17. The method of claim 5,wherein the wireless communication device comprises at least one of: anEvolved Machine-type communication (eMTC) device; and a NarrowbandInternet-of-things (NB-IoT) device.
 18. A method for an uplinktransmission timing adjustment in a wireless communication device servedby a network node and configured to operate in a coverage enhancementmode, wherein the coverage enhancement mode comprises repetitivetransmissions of multiple uplink signals with respective repetitionperiods, the method comprising: aligning the respective repetitionperiods by shifting in time at least one of start or end points of therespective repetition periods according to a predetermined rule, suchthat an overlap time of the respective repetition periods is maximizedor single transmission of the multiple uplink signals is minimized. 19.The method of claim 18, wherein the predetermined rule comprises one of:the respective repetition periods to start at the same time; therespective repetition periods to end at the same time; the respectiverepetition periods to start within a first time duration; and therespective repetition periods to end within a second time duration. 20.A wireless communication device served by a network node and configuredto operate in a coverage enhancement mode, wherein the coverageenhancement mode comprises a repetitive transmission of a first uplinksignal during a first repetition period, the wireless communicationdevice comprising a processing circuit configured to: determine a changein a downlink timing; determine whether the first repetition period isongoing; and, in response to the change in the downlink timing and thefirst repetition period being ongoing, perform an adjustment of anuplink transmission timing outside the first repetition period.
 21. Thewireless communication device of claim 20, wherein the processingcircuit is further configured to: determine a change in a downlinktiming of a reference signal received at the wireless communicationdevice from the network node with respect to a reference time.
 22. Thewireless communication device of claim 21, wherein the processingcircuit is further configured to: determine a relative change of timingof one or more reference signals broadcasted by the network node on thedownlink, to a timing predicted for the reference signals by thewireless communication device based on one or more previous referencesignals.
 23. The wireless communication device of claim 20, wherein theuplink transmission timing is adjusted to within ±Te seconds before anext uplink transmission begins and after the ongoing uplinktransmission period has ended, and wherein Te is indicative of a timingerror limit value and depends upon downlink and uplink characteristics.24. The wireless communication device of claim 20, wherein the coverageenhancement mode further comprises a transmission of a second uplinksignal without a repetition, and wherein the processing circuit isfurther configured to: configure the second uplink signal with a sameuplink transmission timing as that of the first uplink signal.
 25. Thewireless communication device of claim 20, wherein the coverageenhancement mode further comprises a repetitive transmission of a seconduplink signal with a second repetition period at least partly overlappedwith the first repetition period, and wherein the processing circuit isfurther configured to: in response to the change in the downlink timing,perform the adjustment of the uplink transmission timing outside both ofthe first and second repetition periods.
 26. The wireless communicationdevice of claim 20, wherein the processing circuit is further configuredto: if the first repetition period is not ongoing, adjust the uplinktransmission timing to within ±Te seconds before the first repetitionperiod begins, wherein Te is indicative of a timing error limit valueand depends upon downlink and uplink characteristics.
 27. The wirelesscommunication device of claim 23, wherein the uplink characteristicscomprises any or a combination of uplink system bandwidth, subcarrierspacing, symbol length, cyclic prefix length, and wherein the downlinkcharacteristics comprises any or a combination of downlink systembandwidth, and an operation mode of repetition.
 28. The wirelesscommunication device of claim 20, wherein the processing circuit isfurther configured to determine whether the first repetition period islonger than one radio resource time unit, based on one of: downlinkcontrol information (DCI) transmitted by the network node, wherein theDCI contains explicit or implicit information on a number of repetitionsto use for the repetitive transmission of the first uplink signals, andradio resource control (RRC) configuration provided by the network node,wherein the RRC configuration contains a number of resources for thewireless communication device in a radio resource time unit, and whereinthe number of resources explicitly or implicitly indicates the number ofrepetitions.
 29. The wireless communication device of claim 28, whereinthe processing circuit is further configured to, if the first repetitionperiod is not longer than one radio resource time unit, adjust theuplink transmission timing according to a rule comprising the followingconditions: a. a maximum amount of a magnitude of a timing change in oneadjustment shall be Tq seconds; b. a minimum aggregate adjustment rateshall be 7*Ts per second, wherein Ts is a basic timing unit; and c. themaximum aggregate adjustment rate shall be Tq per 200 ms, wherein Tqdepends on downlink and uplink characteristics.
 30. The wirelesscommunication device of claim 29, wherein Tq is mapped on a downlinkbandwidth according to a table of: Downlink Bandwidth (MHz) Tq 1.4 17.5Ts  3 9.5 Ts 5 5.5 Ts ≧10 3.5 Ts


31. The wireless communication device of claim 28, wherein the one radioresource time unit corresponds to one Evolved universal terrestrialradio access network (EUTRAN) subframe or two EUTRAN subframes.
 32. Thewireless communication device of claim 20, wherein the wirelesscommunication device comprises at least one of: an Evolved Machine-typecommunication (eMTC) device; and a Narrowband Internet-of-things(NB-IoT) device.
 33. A method for enhancing an uplink transmissiontiming adjustment procedure for a wireless communication device, themethod comprising: determining that the wireless communication device isto be configured to transmit at least two uplink signals over at leastpartly overlapping repetition periods; and enabling the wirelesscommunication device to align the respective repetition periods of theat least two uplink signals.
 34. The method of claim 33, wherein thestep of enabling the wireless communication device to align therespective repetition periods of the at least two uplink signalscomprises: enabling the wireless communication device to align therespective repetition periods by shifting in time at least one of startor end points of the respective repetition periods according to apredetermined rule, such that an overlap time of the respectiverepetition periods is maximized or single transmission of the multipleuplink signals is minimized.
 35. The method of claim 34, wherein thepredetermined rule comprises one of: the respective repetition periodsto start at a same time; the respective repetition periods to end at asame time; the respective repetition periods to start within a firsttime duration; and the respective repetition periods to end within asecond time duration.
 36. The method of claim 33, wherein the method isperformed in a network node serving the wireless communication device.37. The method of claim 33, wherein the wireless communication device isconfigured to operate in a coverage enhancement mode comprisingrepetitive transmissions of at least two uplink signals.
 38. A networknode configured to enhance an uplink transmission timing adjustmentprocedure for a wireless communication device, the network nodecomprising a processing circuit configured to: determine that thewireless communication device is to be configured to transmit at leasttwo uplink signals over at least partly overlapping repetition periods;and enable the wireless communication device to align the respectiverepetition periods of the at least two uplink signals.
 39. The networknode of claim 38, wherein the processing circuit is configured to enablethe wireless communication device to align the respective repetitionperiods by shifting in time at least one of start or end points of therespective repetition periods according to a predetermined rule, suchthat an overlap time of the respective repetition periods is maximizedor single transmission of the multiple uplink signals is minimized. 40.The network node of claim 39, wherein the predetermined rule comprisesone of: the respective repetition periods to start at a same time; therespective repetition periods to end at a same time; the respectiverepetition periods to start within a first time duration; and therespective repetition periods to end within a second time duration. 41.The network node of claim 38, wherein the wireless communication deviceis configured to operate in a coverage enhancement mode comprisingrepetitive transmissions of at least two uplink signals.